The primary efficacy variable will be the PC20 yielded from AMP airway challenge testing at the three treatment visits. FeNO, sampled at three time points at each treatment period visit, will be a exploratory variable. Safety assessment will include monitoring of adverse events, physical examination, vital signs, EKGs, spirometry, serum and urine pregnancy tests, and laboratory determinations. Blood sampling at a time-point series will provide pharmacokinetics data.